Scotopic retinal adaptation, that in mature retina depends upon both receptoral and post receptoral processes, will be investigated in normal human infants. Complementary results of previous studies employing three techniques --- psychophysical, electroretinographic and puillographic --- have allowed inferences to be drawn about physiological processes that underlie adults' scotopic visual performance. These three techniques will be used to study human infants' rod mediated adaptive processes. Pilot data suggest that young infants' temporal integration and background adaptation are different than in adults. Psychophysical and electroretinographic studies of temporal summation and scotopic background adaptation will be continued to evaluate variability in the estimates of sensitivity, and to refine the description of age-related changes in retinal sensitivity. Spectral sensitivities in various steady state adaptation conditions will be determined using psychophysical and pupullographic methods to assess rod and cone contributions. The pupillographic studies require [a] construction of a system suitable for measuring infants' (1) criterion pupillary responses in background and dark adaptation and (2) pupillary diameter; (The criterion response is an index retinal sensitivity; pupillary diameter is an index of rhodopsin present.) [b] evaluation of the use of pupillography in infants. Pupillography may be especially useful for the study of the dynamic events accompanying dark adaptation. Pupillographic data will permit investigation of the relation of infants' scotopic sensitivity to rhodopsin during dark adaptation. Recovery of ERG b-wave sensitivity after exposure to the same pre-adapting bleaching lights used in the pupillography experiment will provide an independent measure of dark adaptation. During dark adaptation after exposure to weak, non-bleaching adapting lights, recovery of b-wave sensitivity, amplitude and latency will be measured to investigate "neural" components of infants" retinal adaptation. Data from the psychophysical, electroretinographic and pupillographic studies will permit (a) description of age-related changes in human scotopic retinal function against which the performance of future patients may be compared and (b) analysis of contributions of receptoral and post-receptoral processes to human infants' scotopic retinal adaptation.